Dual catalyst system for producing LLDPE copolymers with improved processability

Abstract

Disclosed herein are ethylene-based polymers generally characterized by a density from 0.89 to 0.93 g/cm3, a ratio of Mw/Mn from 3 to 6.5, a Mz from 200,000 to 650,000 g/mol, a CY-a parameter at 190° C. from 0.2 to 0.4, and a reverse short chain branching distribution. The ATREF profile of these polymers can have a high temperature peak from 92 to 102° C., and a low temperature peak from 18 to 36° C. less than that of the high temperature peak. These polymers can have comparable physical properties to that of a metallocene-catalyzed LLDPE, but with improved processability, shear thinning, and melt strength, and can be used in blown film and other end-use applications.

We claim: 
     
       1. An ethylene polymer having:
 a density in a range from about 0.89 to about 0.93 g/cm 3 ; 
 a ratio of Mw/Mn in a range from about 3 to about 6.5; 
 a Mz in a range from about 200,000 to about 650,000 g/mol; 
 a CY-a parameter at 190° C. in a range from about 0.2 to about 0.4; 
 a number of short chain branches (SCB's) per 1000 total carbon atoms of the polymer at Mz that is greater than at Mn; and 
 the following polymer fractions in an ATREF test: 
 from about 0.1 to about 8 wt. % of the polymer eluted below a temperature of 40° C.; 
 greater than about 45 wt. % of the polymer eluted between 40 and 76° C.; 
 less than about 36 wt. % of the polymer eluted between 76 and 86° C.; and 
 from about 1 to about 26 wt. % of the polymer eluted above a temperature of 86° C. 
 
     
     
       2. An article of manufacture comprising the polymer of  claim 1 . 
     
     
       3. The polymer of  claim 1 , wherein:
 the density is in a range from about 0.902 to about 0.922 g/cm 3 ; 
 the ratio of Mw/Mn is in a range from about 3.5 to about 6; 
 the Mz is in a range from about 210,000 to about 575,000 g/mol; and 
 the CY-a parameter at 190° C. is in a range from about 0.24 to about 0.38. 
 
     
     
       4. The polymer of  claim 3 , wherein:
 the ethylene polymer has a unimodal molecular weight distribution; and 
 the ethylene polymer comprises an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, an ethylene/1-octene copolymer, or a combination thereof. 
 
     
     
       5. A blown or cast film comprising the polymer of  claim 4 , wherein the film has an average thickness in a range from about 0.5 to about 8 mils. 
     
     
       6. The polymer of  claim 1 , wherein:
 from about 0.5 to about 7 wt. % of the polymer is eluted below a temperature of 40° C.; 
 from about 46 to about 90 wt. % of the polymer is eluted between 40 and 76° C.; 
 from about 4 to about 35 wt. % of the polymer is eluted between 76 and 86° C.; and 
 from about 2 to about 25 wt. % of the polymer is eluted above a temperature of 86° C. 
 
     
     
       7. An article of manufacture comprising the polymer of  claim 6 . 
     
     
       8. The polymer of  claim 1 , wherein the ethylene polymer has:
 a Mw in a range from about 80,000 to about 180,000 g/mol; and 
 an D3 parameter in a range from about 1.1 to about 1.4. 
 
     
     
       9. The polymer of  claim 1 , wherein the ethylene polymer has:
 a melt index in a range from about 0.5 to about 5 g/10 min; and 
 a ratio of HLMI/MI in a range from about 28 to about 42. 
 
     
     
       10. The polymer of  claim 1 , wherein the ethylene polymer contains less than 0.008 long chain branches per 1000 total carbon atoms. 
     
     
       11. The polymer of  claim 1 , wherein the ethylene polymer is further characterized by an ATREF profile having a first peak and a second peak, wherein:
 the second peak is at a temperature from about 92 to about 102° C.; and 
 the first peak is at a temperature from about 18 to about 36° C. less than that of the second peak. 
 
     
     
       12. An article of manufacture comprising the polymer of  claim 11 . 
     
     
       13. An ethylene polymer having:
 a density in a range from about 0.89 to about 0.93 g/cm 3 ; 
 a ratio of Mw/Mn in a range from about 3 to about 6.5; 
 a Mz in a range from about 200,000 to about 650,000 g/mol; 
 a CY-a parameter at 190° C. in a range from about 0.2 to about 0.4; 
 a number of short chain branches (SCB's) per 1000 total carbon atoms of the polymer at Mz that is greater than at Mn; and 
 an ATREF profile characterized by a first peak and a second peak, with the second peak at a temperature from about 92 to about 102° C., and the first peak at a temperature from about 18 to about 36° C. less than that of the second peak. 
 
     
     
       14. The polymer of  claim 13 , wherein the first peak is at a temperature in a range from about 60 to about 80° C. 
     
     
       15. The polymer of  claim 13 , wherein the first peak is at a temperature from about 20 to about 34° C. less than that of the second peak. 
     
     
       16. The polymer of  claim 13 , wherein the second peak is at a temperature in a range from about 93 to about 100° C. 
     
     
       17. The polymer of  claim 13 , wherein the ethylene polymer has:
 a Mw in a range from about 80,000 to about 180,000 g/mol; 
 an D3 parameter in a range from about 1.1 to about 1.4; 
 a melt index in a range from about 0.5 to about 5 g/10 min; and 
 a ratio of HLMI/MI in a range from about 28 to about 42. 
 
     
     
       18. An article of manufacture comprising the polymer of  claim 17 . 
     
     
       19. The polymer of  claim 1 , wherein the ethylene polymer is an ethylene/α-olefin copolymer further characterized by:
 a density in a range from about 0.902 to about 0.928 g/cm 3 ; 
 a ratio of Mw/Mn is in a range from about 3.2 to about 5.8; 
 a Mz in a range from about 210,000 to about 575,000 g/mol; and 
 a ratio of HLMI/MI in a range from about 25 to about 45. 
 
     
     
       20. The polymer of  claim 13 , wherein the ethylene polymer is an ethylene/α-olefin copolymer further characterized by:
 a density in a range from about 0.902 to about 0.928 g/cm 3 ; 
 a ratio of Mw/Mn is in a range from about 3.2 to about 5.8; 
 a Mz in a range from about 210,000 to about 575,000 g/mol; and 
 a ratio of HLMI/MI in a range from about 25 to about 45.